<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>栅格系统列嵌套</title>
    <link rel="stylesheet" href="./bootstrap/css/bootstrap.min.css">
    <style>
        .row > div {
            height: 50px;
            background-color: pink;
        }
    </style>
</head>
<body>
    <div class="container">
        <div class="row">
            <div class="col-md-4">
                <!-- 我们列嵌套最好加1个行 <div class="row"> 这样可以取消父元素的padding值 而且高度自动和父级一样高  -->
                <div class="row">
                    <div class="col-md-4">a</div>
                    <div class="col-md-8">b</div>
                </div>
            </div>
            <div class="col-md-4">2</div>
            <div class="col-md-4">3</div>
        </div>
    </div>
</body>
</html>